Conventional bolster assemblies normally employ a plurality of layers that are applied at once on a bolster region of interior trim parts of a vehicle, such as an interior door panel, during interior trim part manufacturing. When the bolster assembly is applied to the bolster region of the door panel, the bolster assembly is simultaneously cut as it is glued and pushed into a peripheral groove defining the bolster region. The cutting of the bolster assembly during the manufacturing process increases the amount of scrap material. In addition, if the above process not properly performed, the resulting bolster assembly is defective and the entire interior trim part incorporating the bolster assembly is scraped.
Conventional bolster assemblies may also come in the form of a hand-made “add-on” bolster assembly. The add-on bolster assembly normally includes a heavy substrate layer injection molded to a piece of die-cut foam. A cover skin is wrapped around the periphery of the heavy substrate and die-cut foam, which is then stapled together on the rear side of the bolster assembly. The add-on bolster assembly is then manually attached to an interior trim part by heatstaking, screwing, or by other fastening means, such as palnuts. The weight restrictions and tolerances of the interior trim part results in add-on bolster design restrictions because of the need for the heavy substrate layer. The add-on bolster assembly also is manufactured with a high cost to the manufacturer due to the intensive hand labor. Costs are also increased by the waste of the high amount of scrap material of the die cut foam, as well as the need for extra cover skin material for the stapling operation.
Current profile designs for interior trim parts, such as interior door panels, involve increasing variations in the topography of the door panel because of the varying slopes, surfaces, and grooves of the door panel design. One problem associated with the increasing variation in the topography is that the profile region where the bolster is attached to the groove prevents the bolster assembly from being fully positioned within the groove during the manufacture of the door panel. Another problem associated with conventional manufacturing methods is that relatively large amounts of scrap material are produced, thereby increasing the cost of the interior trim part. Yet another problem associated with conventional manufacturing methods is that consistently manufactured interior trim part is not ensured and the entire trim part is scraped in the event of a malfunction of the manufacturing process.